Old Infinity speakers were tuned without much regard to impedance. I'm not sure which speakers you have, but I've seen a number of crossover upgrades for them you should consider which fixes these issues.
Good as they originally sounded, they were designed without the tools we have today which would allow for simultaneous optimization of frequency and impedance.
Oscillation has nothing to do with whether an amplifier can double power as impedance is halved, and has nothing to do with whether or any such nonsense.
This statement is false, and quoting nobody, your inferring that someone said if an amp can double down to 2ohms, it’s also stable (won’t oscillate)
Can you point to who said this, or is this just a ******* in the wind statement that someone did, I’ve searched and no one has, not even golfnutz who you quoted.
OK, so what is the definition of instability for these Class-D amplifiers?
Stability is the same definition regardless of the kind of amplifier. It is the ability of the amplifier to resist oscillation. Oscillation has nothing to do with whether an amplifier can double power as impedance is halved, and has nothing to do with whether or any such nonsense. Its simply means the amplifier won't oscillate.
Now one thing that potentially could muddy the waters: it is possible to build a class D amplifier that is self-oscillating. This is done using the feedback loop with the intention of using the oscillation frequency in the encoding process of the amplifier. This is a handy technique as it also allows the amplifier to correct for phase shift in the audio passband. But such an amplifier could still be able to oscillate independently of its self-oscillation if there were a design bug! Confusing- but there it is.
@nitrobob - it would appear that V series amp is based on the IcePower 1200AS1/2 modules (not sure if it’s the 1, 2, or combination of both), which has a minimum impedance of 2.7 ohms. They also mention you should use a 20amp circuit for best results.
You might want to consider using a high current stereo amplifier for left and right channels only, and something different for the center, and surrounds.
Very nice speakers but sorry a b***h to drive, neither your amp (mosfet) or a class-D will suffice, they’re just not up to getting the very best out of these Legacy’s
That’s a pretty nasty looking impedance and -phase angle graph. Read back at amps I have suggested and you get the idea of what you need. Doesn’t have to be high wattage 50-100w will do, as those speakers are 95db, BUT!! you need gobs of current all the way down to 2ohms, look at what I say about "almost doubling wattage" for each halving of impedance, then go and search for amps that come close to doing this.
https://www.stereophile.com/images/archivesart/LEG20FIG1.jpg (fig.1) reveals that it needs to be used with an amplifier that can deliver high current into low impedances. Not only are there two minima in the bass of less than 2 ohms, and another of less than 3 ohms in the mid-treble, but there is an amplifier-crushing combination of 3.3 ohms magnitude and 60 degrees capacitive phase angle at 20Hz
You guys have me thinking. I’m not at all on your level of knowledge. So now is a good time for me to throw this out there. I have Legacy Focus mains, with Legacy Marquis center and a nice pair of Ascend Acoustics Sierra 2 raal surrounds. Couple of 18 inch subs also. We do up some video concerts while entertaining, classic rock mainly, and volumes stray up over 110 db ( at 10 feet ). The sound in that room is phenomenal. I had a new ATI Signature 6005 series amp, and occasionally the right channel would just quit. I called ATI. They were really nice about it and explained that probably the Legacy’s were dropping below 2 ohms and tripping the channel. ATI then called Legacy and found out that they indeed did go down to 3 during certain conditions. ATI replaced the board with one that could take more punishment, no questions ask. Here’s my question. Legacy has just released their "V" series amps. They are D series with Ice technology. It's double the output of my ATI. 600 verses 300 per channel . It sounds like a perfect fit to me. Any drawbacks ? Please don’t scold me on the effects of loud listening. I’m 64, been racing cars and enjoying loud hobbies my entire life. Too late to cradle myself now .. Thanks for any input.
dsper Back to the OP’s question What Class D amps will drive a 2 ohm load into his Thiel CS5’s
The proof is in the two posts done here, about Class-D and it’s ability to perform/drive "optimally" into hard loads full range, (not just to be stable!!) even with one of those speakers being very efficient at over 90db!!!
When are the Class-D spruikers going to stop trying to push them like they’re the total answer to amplification, and sell them for what they are, good for easy/medium loads and not hi-end "yet", like Agostino, Gryphon, Solution, Boulder ect ect for driving the types of speaker discussed here, and the topic of this thread!!!!!!!
OK, so what is the definition of instability for these Class-D amplifiers? Since they have over current protection mode, and soft clipping capabilities the amp continues to operate, but not optimally. Without the use of an LED display to the circuit board (1200AS2 has this option), how would you even know it’s happening - is bad sound is the only way? Again, since the amp is running and making music, would this indicate it’s stable?
You are applying criteria that could be used as a measure of a Linear amplifier to a Class-D amplifier which can current limit cycle by cycle, hence the current limit and power limit of a Class-D amplifier can be decoupled rendering your statement irrelevant depending on the Class-D implementation.
It needs to be able to almost double it’s "full" rms wattage for each
halving of impedance, from 8 to 4 and from 4 to 2ohms, and I asked
Merrill twice, to supply that, and twice the question wasn’t answered.
'Stability' is that which prevents the amp from oscillating. Just so you know. So in the phrase:
As I said above, so is an 80’s NAD3020, stability is needed,
- the term is being misused. In fact its unclear what is meant here. Are you saying that the NAD goes into oscillation when presented with a 1 or 2 ohm load??
As I said above, so is an 80’s NAD3020, stability is needed, but that is not the criteria for it to sound good at those types of speakers low impedance’s.It needs to be able to almost double it’s "full" rms wattage for each halving of impedance, from 8 to 4 and from 4 to 2ohms, and I asked Merrill twice, to supply that, and twice the question wasn’t answered.
just call Merrill and ask him if they’ll drive the Kappa 9s.
Ask him more so will they drive the Kappa’s to their very best, seeing they are very expensive amps. See if he’s a saint or a car-salesman.
Buy a pair of pre-owned Merrill Veritas for $5K, they're stable down to 1 ohm. If you're unsure, just call Merrill and ask him if they'll drive the Kappa 9s.
golfnutz Pretty much what I expected. Your experience is basically the same as my except I was using the IcePower 1200AS/2 modules (2.7 ohm rated) with Wilson Watt/Puppy’s. I believe you were using the 1200ASP modules (2 ohm rated). Not just the bass, but I noticed it in the midrange as well. It became very sterile to the point I couldn’t listen anymore. Stereophile also uses the word ’Anemic’
And the Wilson’s are over 92db efficient, but also have a nasty amplifier loading. Same happened to you as I posted above to the Kappa’s. And your 1200AS2 Class-D modules are said to be even better🤦♂️
Stereophile also uses the word ’Anemic’ to describe this behavior when an amp is under powered for a given pair of speakers - which I think is a good descriptive. I tried using subwoofers to ’fill-in’ more musicality, but it really didn’t help that much either.
This is classically what happens to "some" Class-D owners "with hard to drive speakers", that is to get a sub to give some more bass weight and to flesh out the lower/mids and mids more, but it doesn’t cure the problem fully
joysjane At lower levels the music seemed to have lost weight/slam/punch. This loss was in the lower frequencies. As the volume went up the bottom seemed to increase but, the Kappa 9’s sounded anemic. After 2 minutes I get some very loud snaps coming out of my EMIT K & SEMIT K drivers on the left channel speaker.
I rest my case.
At 625W!! into 8 ohms, and 1225W!! into 4ohms and "said to be stable into 2ohms". They didn’t wattage clip, they have no drive into 2ohms.
It wouldn’t have mattered if these Kappas had the 3000w Behringer on them, same thing would have happened "no current, no 2ohm drive, no music".
They didn’t wattage clip or soft clip as atmasphere would have you believe, they just can’t handle the load and current that they were asked to give, and it’s what I’ve been saying all along.
Even a $199 1980’s NAD 3020 integrated "is stable into 2ohms", there’s more than just that, it needs to "almost double" or "greatly increase" it’s clipped" 4ohm wattage into 2ohms also (not just from 8ohms to 4ohms), and that why that spec need to be independently tested "if" ever given.
This is why a pair of old Mark Levinson ML2 monoblocks which are only 25w!!!! into 8ohms!! would have been able to drive these Kappa’s beautifully full range to a certain volume level, as they are only 25w, but they can close to double all the way down to 1ohm it’s said. 8ohm 25w 4ohm 50w 2ohm 100w 1ohm 200w
Rather than saying from an earlier post, I'll just paste it in again (from the spec sheet):
Overload Protection - In case of high-amplitude continuous low frequency signals in loads lower than 4 ohms the power supply may not be able to deliver the required amount of power to the amplifier and the supply voltage will drop. The overload protection circuit will then lower the threshold of the input soft clipping circuit until the output power has been reduced to an acceptable level. As a result the amplifier will not shut down because of under voltage and the music will still be playing but with a softly shaped audio signal.
Pretty much what I expected. Your experience is basically the same as my except I was using the IcePower 1200AS/2 modules (2.7 ohm rated) with Wilson Watt/Puppy's. I believe you were using the 1200ASP modules (2 ohm rated). Not just the bass, but I noticed it in the midrange as well. It became very sterile to the point I couldn't listen anymore. Stereophile also uses the word 'Anemic' to describe this behavior when an amp is under powered for a given pair of speakers - which I think is a good descriptive. I tried using subwoofers to 'fill-in' more musicality, but it really didn't help that much either.
One thing you can say about the B&O Icepower modules, and I give them credit, they really do try hard to keep things going even in Overload Protection (no blown fuse).
I don't know what a Class D amp sounds like when clipping.
That depends very much on how the amp is designed. Some soft clip and some don't- some 'snap' when they clip. You really don't want to do that with a powerful amp- the tweeters are at risk!
I want to add something to the Class D monos driving my Infinity’s...
With the noticeable lack of bass at lower volumes I must pose a thought I’m having. Is the lack of bass/bottom caused by the crazy impedance load of the Kappa 9’s when being driven by these amps?
I have a pair of Legacy-Audio Focus speakers tucked away. They do not lack any bottom end with any amps I’ve driven them with... maybe because they’re a much more efficient speaker than the 9’s might that bottom return with these Class D amps? I don’t know.
Y'alls thoughts regarding the impedance of the Kappa 9's...
Maybe one of these days I can wrestle those heavy bastards out and hook up the SX’s. Kinda doubting that will happen as I’m not getting any younger or less broken.
I was really hoping the Class D amps would provide this. I’m gonna start reducing the amount of gear I have and would have loved amps the size and weight of these Class D’s. I could have moved them around easily. But, the Infinity’s are staying... the rest are going bye-bye.
So, I now have to carry those heavy/awkward Phase Linear Clair Bros WOPL amps back up the stairs and re-configure... Damn!
One more thing, about my cables in the system that was tested... Cardas Golden Reference power cables, Monster Sigma Interconnects with Monster Sigma Speaker cables (ME2’s). Not junk cabling for sure.
Bahahahaaaaa... You's are funny, got me laughing. House is still standing.
What happened... The wife called me saying the boxes arrived. She then asked me, there's amps in these two boxes? So, had to explain what they were, why they were so small and why they weighed next to nothing. All I got was an ok.
Removed the WOPL 700's and hooked up the SX-1000's. I let the amps play on a repeat cd at a low level with the Kappa's in the "Normal" switched position starting early in the morning. Let that roll until 3:00 in the afternoon. Time to start listening...
At half volume I listened for about an hour. All was ok so, time to crank it up. Turned up the volume to 3/4 on the Oppo (the 105D is driving the amps directly). Listened for another 30 minutes and all is still ok. Time to get down to amp-busting' Kappa 9's, lowered the volume to 1/4 and switched the speakers into "Extended" mode. I've put many of my amps into protection mode with the Kappa's in "Extended" mode. Being a little leery of these tiny amps I started out at 1/4 volume listening to various CD's, SACD's and DVD-A discs. All is well after 30 minutes so, time to crank it up a bit. At 1/2 volume now, stayed at this level for an hour while checking if the amps were getting warm. This is the point of no return for many amps I've tried. Half volume and up with the 9's in "Extended" mode is a brutal test for any amplifier.
Ok, I'm starting to get curious. I'm getting up and down, feeling the amps to see if there's any sign of temperature increase. Feeling the sides, the top, the front & back... no temp increase. In comes the wife from running around town. I haven't given my assessment of the sound for a reason. It will come later. I'm listening, the wife walks in and is looking at the speakers with a puzzled look on her face. She turns to me and says... what's wrong with speakers? Something's missing, I don't like it. That's the extent of her ability to evaluate what she hears. More on this later...
Time to turn the volume up to 3/4 and listen. Put in some dynamic music... John Lee Hooker's "BOOM BOMM" 24/96 DAD. The SX-1000's are still pushing the Kappa 9's in "Extended" mode. Many amps have shut down at this point and, only a few have passed the next level test. Volume up to 100% and let's have a go. After 2 minutes I get some very loud snaps coming out of my EMIT K & SEMIT K drivers on the left channel speaker. Right channel speaker ok. Wife comes running in from the kitchen asking what was that? I got to the volume control as quick as possible and turned the system down. CRAP!!!
Not sure what happened. I have the protection on my crossovers by-passed. Have never had this happen. I looked at the EMIT & SEMIT drivers on the left speaker to see if there was any arcing visible on the membranes. Nope, all looked normal. Let everything rest for a half hour and then started bringing up the volume. Wanting to make sure I didn't fry something. Music came back as before. Whew... hoping I dodged a bullet.
I want all to know that I'm in no way a qualified listener/evaluator of equipment and/or speakers. I also can't give any measurements of what this listening session produced... to/for ME. What I am is a person who enjoys his system and the music that's played on that system. I do know what my system sounds like and feel I can give an accurate blah blah of what I heard.
Now let's get to the sound produced. And also to what the wife had observed. At lower levels the music seemed to have lost weight/slam/punch. This loss was in the lower frequencies. This is exactly what my wife had heard. She's not sure what was missing but, she knew something was missing. I didn't prod her or guide her for an explanation but what she said was "Where's the bass"? As the volume went up the bottom seemed to increase but, the Kappa 9's sounded anemic. These Infinity's are everything but anemic!
I also found the same thing when driving the amps with my DV-AX10. Just to make sure it wasn't the Oppo producing what I was hearing.
I'm gonna be the first to say I didn't think these amps had a chance. I was surprised my Infinity speakers didn't throw the amps into protection mode... I did try. In no way did I think they could drive one of the most difficult speaker loads ever produced... they did. When I heard those loud snaps... I'm not gonna say that the amps started clipping at full volume. I do know what other amps sound like when clipping, I don't know what a Class D amp sounds like when clipping.
joysjane: "Stay tuned for my first-hand experience as to how these amps drove my original un-modded Infinity Kappa 9's. One of the amp killing speakers..."
Hello joysjane,
Wow, a teaser on the W4S SX-1000 class D amps and how they worked driving your very low impedance load and notoriously difficult to drive Infinity Kappa 9 speakers. Full details next on News at Eleven? Off the record, on the Q.T. and very hush-hush?
Very tantalizing, great job! You got me hooked, I'm certainly not touching that dial. Drum roll, please?
Agreed. While there's currently no such thing as a class D input stage there is a company, Mola Mola, that offers a class D preamp and pair of class D mono-blocks that have output and input stages specifically designed to perform optimally when used together; the preamp is called the Makua and the matching mono-block amps, based on Hypex NCore 1200 power modules and and smps (switch mode power supply),are called the Kalugas. The part owner and chief designer of Mola Mola, Bruno Putzeys, is also the inventor of ucD (universal class D) as well as class D Hypex NCore technology. He designed the Makua and Kalugas, as well as a unique and optional class D internal dac board for the Makua, that are designed to specifically perform optimally with each other. I'm planning on buying pre-owned examples of all 3 of these Mola Mola products, which have all received numerous excellent professional reviews, within the next monthor so for about $12-14K. I'll post my impressions on all 3 of these once I have adequately had the listening time to form them. I'm sure you'll be awaiting my thoughts with bated breath.
My question is why, knowing all the above, you even bothered to make it?
It features a custom designed, class-A, input stage
Why even mention it on a class-D amp like it’s "special" (it features!!), as all amps have "class-a inputs" is what I refer to, no one in their right mind would make an input stage Class-B!!
George: "Every amp I know of also has Class-A input stages, and "why suddenly is the Class-A linear the preferred way for the input", why not for the output as well???"
Hello George, I don't think anyone's claiming a class A input stage isn't an excellent typology for an input stage since the class A typology is well known for it's very high sound quality performance. At low preamp stage input voltages, the excess heat generated by the highly inefficient class A typology circuitry constantly being in operation is not a major cause for concern. While the extremely inefficient class A typology for an output stage is also excellent for sound quality, the excess heat generated by the highly inefficient class A typology circuitry constantly being in operation is definitely a major cause for concern since it's easily able to significantly raise the temperature in a typical domestic room. But you already knew all this, George, before you made your comment. My question is why, knowing all the above, you even bothered to make it? Obviously, one of the major advantages of utilizing class D output stages rather than class A output stages is its electrical efficiency and resultant dramatic decrease in the amount of electricity that is wasted by simply being converted to excess heat. Class A is about 10% efficient and class D is in excess of 90%. Class A amps are typically expensive, operate at very high temperatures,are very large and heavy due to the numerous, large and heavy heat sinks required in an attempt to dissipate the large quantities of excess heat produced as a result of their extreme electrical inefficiency. Class D amps are typically less expensive, operate at much lower temperatures, are much smaller and lighter due to the their lack of need for heat sinks required to dissipate the very small quantities of heat produced as a result of their extreme electrical efficiency. The difference can be demonstrated clearly by a raw egg. Drop one on a class A amp at peak operating temp and you'll shortly produce a fried egg. Drop one on a class D amp at peak operating temp and you'll just have a raw egg mess that will remain until you decide you may want to clean it up. Besides the advantage of your amp not acting as an HVAC component, there's also the class D advantage of cooler operating temps likely resulting in improved reliability and longevity due to the well known principle that sustained excess heat is a major factor in electrical component part failures. However, I believe an individual's amp choice is likely made primarily on the basis of perceived sound quality and price to performance ratios, with amp typology traits being less important to most. I think Class D amps need to be leaders on these two factors to achieve continued success.
It features a custom designed, class-A, input stage
Every amp I know of also has Class-A input stages, and "why suddenly is the Class-A linear the preferred way for the input", why not for the output as well???
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For a ten foot run I suspect that difference in gauge may well be audible with a low impedance load like that. With respect to interconnects- hard to say. The differences I've heard in interconnects are unrelated to brightness caused by increased distortion in amplifiers.
I have been thinking about what you wrote earlier in this thread: "...all amplifiers regardless of technology have higher distortion into 2 ohms which is audible as increased brightness and harshness. You can see this in the specs (if 2 ohms distortion is even specified, but you can also see it in the 4 ohm spec as opposed to 8). Further complicating matters is the critical nature of the speaker cable, which must be kept very short and also must have a fairly heavy gauge. At that impedance its very easy for the cable to contribute to the overall source impedance seen by the loudspeaker!
In a nutshell, 2 ohm loudspeakers are impractical and the ability to drive a load like that is over-rated..."
So...a couple of layman's questions:
1. Does this mean that differences between interconnects would be more discernible in a system that did not need to handle a 2 ohm load or is it that one would simply hear a different version of "brightness and harshness" ion a less efficient system? Bear in mind that I have never critically listened to a high efficiency system and probably do not understand transparency in the same way that you might.
2. What is your opinion about ten or twelve gauge stranded copper wire as a speaker cable for Thiel CS5's? Is it even audible for ten foot run compared to fourteen or sixteen gauge?
Hey George, Here's a start to explaining of what @atdavid is talking about
https://www.stereophile.com/reference/707heavy/index.html You can see that because class D amp output devices are either on or off, there isn't a portion of their operation that is in the linear region. As a result you don't have high dissipation in the output device at some portion of the waveform that the amplifier is amplifying.
Based on your responses to atdavid so far it appears that you didn't at least use Google to help you out on this one. Here's a tip from from a well-known Greek individual known as Aristophanes:Youth ages, immaturity is outgrown, ignorance can be educated, and drunkenness sobered, but stupid lasts forever. So whats it going to be? Please try and follow along instead of promoting fake news. Google is your friend- before going off on your rabbit hole theories, just try and see if you can find out about it first.
Only this and also being stable will indicate what’s going with an amp,
into serious low impedance’s as the OP’s and many other hi-end speakers
have.
I noticed this comment- what do you mean by being stable? 'Stability' is generally used in the context of a circuit's resistance to oscillation. Somehow I don't think that's what you meant, but just for the record all of our amps are stable into into any load impedance included a dead short. IOW you can't set them into oscillation regardless of the load condition. But you meant something else didn't you? Again Google is your friend:https://www.google.com/search?client=ubuntu&channel=fs&q=amplifier+stability&ie=utf-8&am...As you can see, stability has to do with oscillation, not anything else.
C’mon George, are you actually implying that a pair of the 1 ohm stable, 800 watt and highly praised Merrill Veritas mono-blocks won’t make much music on the OP’s
Read what I wrote, not what you think or wish I wrote, your just as bad as the other *******.
jetter, I have no skin in the game for Class-D, AB, or A. I am just the guy that actually understands what EPDR is, and why it does not apply to Class-D amps, and why it is particularly harsh to BJT amps, the type that a certain person pushes as the holy grail for low impedance, citing EPDR. I and Noble100 have given examples of amplifiers proven to work, and work well at 2 ohms.
Here is an independent post from DIYAudio. That "max-current-limit", something a Class-D amplifier can do on a cycle by cycle basis, explains why you can design a Class-D amp with a derated 2 ohm output power without impacting sound quality. The statement about SOA (safe operating area) goes back to the EPDR, or why it is not applicable to Class-D. You will find similar posts on the Internet from people with a good understanding of the technology.
There is another thing that comes into play:
Because of the working principle there is no need for SOA protection
like it is used with linear amps. Max-current limit is absolutely
sufficient. This gives these amps the ability to drive quite "cruel"
loads with ease. The bass reproduction of some class-d amps is really
stunning. Not that they are doing megabass compared to linear ones but
they reproduce bass in a very clean and effortless way.
It's apparent that georgehifi has appointed himself the official judge on this thread who administers the amp typology scales of justice with a big, heavy thumb on a particular scale and applies amp typology justice and fairness in the manner of a 15th century sadistic Russian czar.
georgehifi: "Yes, they may be stable that’s only half of the equation, so is a $199 30w NAD 3020 integrated from the 80’s, it’s also "stable" at 2ohm loading, and also on the OP’s Thiel CS5’s, won’t make much music though."
C'mon George, are you actually implying that a pair of the 1 ohm stable, 800 watt and highly praised Merrill Veritas mono-blocks won't make much music on the OP's Thiel CS5s? Here's a link to just one of a plethora of highly positive reviews on the Veritas and their music making abilities:
The whole basis of your reasoning is that if the power does not double from 8 ohms to 4 ohms, and then again from 4 to 2, that it couldn't possible work right. There is no way you can make that determination without knowing exactly why a specific power limitation may exist at 2 ohms, and you definitely cannot use whatever logic you may think applies to a linear amplifier to a Class-D.
Merrill said all of his class D former Veritas and new Element amps are stable down to 1 ohm, George.
Yes, they may be stable that’s only half of the equation, so is a $199 30w NAD 3020 integrated from the 80’s, it’s also "stable" at 2ohm loading, and also on the OP’s Thiel CS5’s, won’t make much music though.
But when I ask him "twice" to produce "true" rms wattage figures (preferably measured by an independent lab) just before clipping at 8, 4, and 2ohms, I was "then" met with a deafening silence.
Only this and also being stable will indicate what’s going with an amp, into serious low impedance’s as the OP’s and many other hi-end speakers have.
Just got done talking with Merrill of Merrill Audio. He says a lot of his customers are trading in their $12K Veritas mono-blocks on his new line of Element amps with GaN FETs. He said the older GaNs sound better than the newest ones, interesting.
I've decided to buy a pair of pre-owned class D Veritas from him at less than half price, I'm going to pair them with a Levinson 326S preamp, Lumin D2 dac/streamer, Oppo 205, all balanced cables and Magnepan 2.7QR speakers.
Merrill said all of his class D former Veritas and new Element amps are stable down to 1 ohm, George. Dsper, a $5K pre-owned pair of Veritas would be an ideal amp solution for any Thiels, Kappas or Apogees you care to use.
Now if only there were Class-D amplifiers that drove into 2 ohms without any trouble like the op asked ... oh, there are. Cherry Class-D do. Mytek will as well. There is nothing "sexy" about them, they just do the job they are designed to do. Obviously you have heard them with difficult to drive speakers?
Once again, yes it does sunshine, as you both push the class-d BS, that it can drive
the speaker loads were talking about here as the OP (
Thiel CS5)
speakers as good as the best BJT amps
can
This is a class-D thread. No one is pushing anything. I am stating, quite clearly, that your "push" of EPDR as a relevant value is meaningless w.r.t. Class-D amplifiers. Given that EPDR is meaningless, we don't need to consider 0.9 ohm loading as you have pushed for the Alexia as it has not meaning within a Class-D discussion. The standard impedance which does not dip below about 2.5-2.6 ohms, is the relevant value for discussion.
BJT has nothing to do with a Class-D discussion, but since you bring up EPDR, EPDR is most damaging to a BJT amplifier in real world conditions because of secondary failure that MOSFETS, and tubes do not experience.
Yes it does sunshine, as you both push the class-d BS, that it can drive the speaker loads were talking about here as good as the best BJT amps can, and the biggest laugh your mate says his OTL’s can drive the Alexia’s nicely.
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